There are a lot of tutorials out there covering these styles, commercial and free. Watch a few and buy whatever they are using. Not because these synths will the best and you would fail should you use anything else but if you aren't very advanced in production following a tutorial is much easier if you are using exactly the same tools.
I suspect that will be mostly Serum, for trance it's also Sylenth or Spire (afaik Ottaviani uses Spire himself despite he's mostly a hardware guy) for techno - also a Moog-esque synth, such as Monark/Arturia/Diva etc
Yes and no. In theory you can recreate any Sylenth preset in Dune, in practice I recreaded a bunch of my favourite patches and found that Sylenth has some interesting sonic nuances in filter/unison/distortion etc which are hard to nail exactly in Dune. Sylenth is a kind of "sweet spot machine", some call it dated, some call it classic
Often compared but not really compartable IMO. I've got a Snow (the same engine as TI2), D3 has a lot of similarities in features and signal flow but to me they sound nothing alike. For a dedicated Virus emulation try Viper if you are on PC. Oher synths that aren't meant to be Virus emulations but have somewhat similar overall sound character are Spire and Hive2.
Sure you can make trance/techno with Dune3 but I think it's more popular among ambient or soundtrack producers, it's strongest point are pads, mellow ambient sounds and classic analog leads IMO.
Yes, in a way. It doesn't have much special features but it's very easy to use and has a nice sound, also you can find preset packs relevant to your genres from Sonic Academy themselves.
More a dedicated wavetable VST but a really comprehensive one. Unlike Dune it uses a universal wavetable format so it's much easier to find 3rd party wavetables compatible with Serum. Also it has a bunch of "warp" (wavetable effects) modes which Dune3 doesn't have (I think that's more relevant to psytrance or "wub wubs" but I may not know some techno or mainstream trance specific sounnd design tricks as I don't make these genres).
Serum has been around for much longer. They share a lot of similar features but I find Serum sounding more hi fi, especially if you use FM, sync and distortions (again, this is probably more relevant to the genres that use a lot of sci fi SFX stuff like psytrance).
